1. Technical Field
This invention relates to a laser for generating an optical comb.
2. Discussion of Related Art
Lasers which serve to generate an optical comb for use in, e.g., optical wavelength-division multiplex systems are known in the art. For instance, an article by N. Park et al, "24-Line Multiwavelength Operation of Erbium-Doped Fiber-Ring Laser", IEEE Photonics Technology Letters, Vol. 8, No. 11, November 1966, describes an erbium-doped fiber-ring laser in which the individual wavelengths are selected via a Lyot filter incorporated in the ring resonator. At low temperatures it is then possible to obtain an optical comb in the range of 1535 to 1560 nm. At room temperature, only few wavelength peaks are obtainable since at such a temperature and with a conventional resonator design, the criterion "ring gain equal to unity" cannot be met for many wavelengths, because the gain is wavelength-dependent. Under the circumstances, simultaneous oscillation of just a few lines is only possible in a narrow wavelength range. Cooling the fiber to liquid nitrogen temperature, e.g., for use in a commercial transmitter, is impractical and very expensive.